The BlockChain of custody?
I guess you could call it so, indeed.
PS. After more thinking, it appears to me this scheme is not sufficient to prevent double spending.
But it's probably not too far from what should be done.
PS#2. One solution might be to code the PGP fingerprint into the amount.
Here is my GPG fingerprint for instance
3617 0FB4 863D 595A 6E47 0EB6 AB5E F7EF 50B8 0E68
I can easily convert it into 10 integers smaller than 16**4 = 65536.
for i in 3617 0FB4 863D 595A 6E47 0EB6 AB5E F7EF 50B8 0E68
do echo $((0x$i))
Which gives :
I can turn these numbers into amounts bigger than 0.01 BTC. I have to do that otherwise the message could be corrupted by mining fees.
for i in 13847 4020 34365 22874 28231 3766 43870 63471 20664 3688
do echo 0.0$((10**6 + n++*16**4 + i))
I use the $n number in order to give a sequencial order to these number. It is necessary since I doubt there is any sequential order for transactions inside a same block.
Then, all I have to do is to send these amounts to the bitcoin address made out of a signed declaration sayin that I've sold my asset to someone, without saying who exactly.
The advantage is that a receiver of the asset can then check that it has not been sold to someone else before. In the previous scheme this was not possible if the former receiver doesn't claim the asset.
Such a transaction would cost between 0.1 BTC and 0.1 + 45*16**4 + 10*16**4 = 0.12949120 BTC
That might be a bit too expensive.